Background

In 1861, Bazin gave the name erythema induratum to a nodular eruption that occurred on the lower legs of young women with tuberculosis. In 1945, Montgomery et al, while fully acknowledging the existence of tuberculosis-associated erythema induratum, coined the term nodular vasculitis to describe chronic inflammatory nodules of the legs that showed histopathologic changes similar to those of erythema induratum, that is, vasculitis of the larger vessels and panniculitis.

Erythema induratum and nodular vasculitis had been considered the same disease entity for a long time. However, nodular vasculitis is now considered a multifactorial syndrome of lobular panniculitis in which tuberculosis may or may not be one of a multitude of etiologic components. Therefore, erythema induratum/nodular vasculitis complex is classified into 2 variants: erythema induratum of Bazin type and nodular vasculitis or erythema induratum of Whitfield type. The Bazin type is related with tuberculous origin, but Whitfield type is not.

Motswaledi and Schulz
[2] noted that erythema induratum of Bazin, lichen scrofulosorum, and papulonecrotic tuberculide are the 3 recognized tuberculides, which are sequelae of immunologic reactions to hematogenously dispersed antigenic components of Mycobacterium tuberculosis. A fourth tuberculide, called nodular granulomatous phlebitis, is distinct from erythema induratum.

Pathophysiology

The morphologic, molecular, and clinical data suggest that erythema induratum and nodular vasculitis represent a common inflammatory pathway, that is, a hypersensitivity reaction to endogenous or exogenous antigens. One such antigen is the tubercle bacillus. Patients with erythema induratum have a positive tuberculin skin test result and a marked increase in their peripheral T lymphocyte response to purified protein derivative (PPD) of tuberculin, which can cause a delayed-type hypersensitivity reaction. Results from the enzyme-linked immunosorbent assay–based IGRA (QuantiFERON-TB Gold In-Tube, Cellestis; Victoria, Australia) blood test for tuberculosis commonly are positive in patients with erythema induratum, again suggesting that that erythema induratum is a hypersensitivity reaction to a systemic infection.

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Epidemiology

Frequency

United States

Isolated cases of erythema induratum have been reported in the United States.

International

While nodular vasculitis is quite common, particularly in Europe, erythema induratum is rare in Western countries. Erythema induratum is still prevalent in India, Hong Kong, and some areas of South Africa. Erythema induratum was the most common (86%) form of cutaneous tuberculosis (tuberculid) in Hong Kong found between 1993 and 2002
[3] and was mostly found in women and mostly on the legs. In this period (1993-2002), 127 patients with erythema induratum out of a total of 147 patients with either cutaneous tuberculosis or tuberculids were reported.

Sex

Erythema induratum shows female predominance, and lower extremities are the most common sites in both male and female patients; however, it also may occur in other areas.

Age

Erythema induratum most commonly affects women aged 20-30 years. The condition is more common in young women than in other people, but it may occur later in life.

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Prognosis

The prognosis is good if treated properly. To date, no fatal cases of erythema induratum have been reported. However, the chronic, recurrent, painful nodules and resultant scarring can be a source of significant morbidity.

The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous previous authors, Beom Joon Kim, MD, and Kwang-Hyun Cho, MD, to the development and writing of this article.